Question

• About errors that can occur in the process of meiosis, and several types of errors are mentioned. Select of these types of errors (e.g. chromosome number, non-disjunctions, etc.) and provide a brief description of the error. Then do a little bit of online research related to the type of error and identify and describe one disease or condition that can result from this type of error (example – Trisomy 21 is where there is an extra chromosome in the 21^st pair, and is responsible for the condition of Down Syndrome). Be sure to describe the symptoms and any treatments that are associated with the condition you select.
• The concept of DNA replication is a complicated one – and often pretty difficult for us to visualize/grasp. In your post, identify:
  • One aspect of process of the DNA replication that the video/animation does a good job of describing, or that made things easier to understand (for instance, if you didn’t understand what Okazaki fragments were and the video helped explain it, describe what makes the concept more understandable in the video/animation)
  • At least one aspect of the process that you are still not quite grasping (that’s ok if more than one, it’s complicated!)

Answer 1

1) Meiosis is the cell division that reduces the number of the chromosome number by half. This creates 4 haploid daughter cells. Meiosis occurs in all sexually reproducing organisms. There are 8 eight stages in the process of meiosis. They are prophase I, prophase II, Metaphase I, Metaphase II, Anaphase I, Anaphase II, Telophase I, Telophase II and cytokinesis.

Errors can occur in the chromosome number during meiosis. Errors during meiosis can cause mutations in gametes. The main error occurs during meiosis is chromosomal non -disjunction. This results in the wrong number of chromosomes in sex cells. Sometimes in exceptional cases, the chromosome number may increase or decrease. If an extra chromosome for a particular pair increases, then there occurs a condition called trisomy. If there occurs a decrease in 1 chromosome, then there occurs a condition called monosomy.

Klinefelter's syndrome is a condition or defect caused by an increase in 1 sex chromosome in a male. Klinefelter's syndrome results in spontaneous miscarriage in the first trimester. The sex cells of the person with this syndrome are XXY.

Common symptoms of this disorder are breast enlargement in males, delayed puberty, infertility, osteoporosis, reduced sex drive, low set ears, etc.

Treatment of Klinefelter's syndrome includes testosterone replacement therapy, breast tissue removal, fertility treatment, etc. The majority of men with Klinefelter's syndrome are not fertile.

2) DNA replication is the process in which DNA makes a copy of itself. This copy is made in cell division. It produces 2 identical replicas of DNA from 1 original DNA. It is the basis of biological inheritance. There are 5 steps in DNA replication. They are unzipping 2 single strands, initiation, elongation and termination.

DNA replication is done to make a copy of DNA and this copy is for the new daughter cells formed. If replication of DNA will not occur, then the newly formed daughter cells lack hereditary fabric to give instructions for creating proteins that are responsible for body functions.

Okazaki fragments are short sequences of DNA nucleotides. These fragments are linked together by enzyme DNA ligase to create a lagging strand in the process of DNA replication.